Topic
Visual cryptography
About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.
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TL;DR: A (k, k) RG-based EVCS that needs neither extra pixel expansion nor any basis matrices (codebook), which are inevitable in conventional solutions of EVCS is presented.
52 citations
TL;DR: A set of encryption codes is developed to maintain the designed viewing zone and a display is demonstrated that provides a limited viewing zone that ensures the security of visual information.
Abstract: We propose a secure display technique based on visual cryptography. The proposed technique ensures the security of visual information. The display employs a decoding mask based on visual cryptography. Without the decoding mask, the displayed information cannot be viewed. The viewing zone is limited by the decoding mask so that only one person can view the information. We have developed a set of encryption codes to maintain the designed viewing zone and have demonstrated a display that provides a limited viewing zone.
51 citations
TL;DR: An improved definition for visual cryptography is proposed based on an observation, in which the revealed images may be darker or lighter than the backgrounds, and which shows that visual cryptography schemes based on this definition indeed have better pixel expansion in average.
Abstract: Visual cryptography is to encrypt a secret image into some shares (transparencies) such that any qualified subset of the shares can recover the secret “visually.” The conventional definition requires that the revealed secret images are always darker than the backgrounds. We observed that this is not necessary, in particular, for the textual images.
In this paper, we proposed an improved definition for visual cryptography based on our observation, in which the revealed images may be darker or lighter than the backgrounds. We studied properties and obtained bounds for visual cryptography schemes based on the new definition. We proposed methods to construct visual cryptography schemes based on the new definition. The experiments showed that visual cryptography schemes based on our definition indeed have better pixel expansion in average.
50 citations
05 May 2013
TL;DR: This paper proposes a method for processing halftone images that improves the quality of the share images and the recovered secret image in an extended visual cryptography scheme for which the size of the shares and the recoverable image is the same as for the original halftones secret image.
Abstract: Visual cryptography is a secret sharing scheme which uses images distributed as shares such that, when the shares are superimposed, a hidden secret image is revealed. In extended visual cryptography, the share images are constructed to contain meaningful cover images, thereby providing opportunities for integrating visual cryptography and biometric security techniques. In this paper, we propose a method for processing halftone images that improves the quality of the share images and the recovered secret image in an extended visual cryptography scheme for which the size of the share images and the recovered image is the same as for the original halftone secret image. The resulting scheme maintains the perfect security of the original extended visual cryptography approach.
50 citations
TL;DR: The proposed flip visual cryptography scheme is proved to have conditionally optimal contrast: its contrast is optimal if the double-secrets non-expanded FVC scheme is required to have perfect security.
50 citations